{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Copyright 2014 Brett Slatkin, Pearson Education Inc.\n",
    "#\n",
    "# Licensed under the Apache License, Version 2.0 (the \"License\");\n",
    "# you may not use this file except in compliance with the License.\n",
    "# You may obtain a copy of the License at\n",
    "#\n",
    "#     http://www.apache.org/licenses/LICENSE-2.0\n",
    "#\n",
    "# Unless required by applicable law or agreed to in writing, software\n",
    "# distributed under the License is distributed on an \"AS IS\" BASIS,\n",
    "# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n",
    "# See the License for the specific language governing permissions and\n",
    "# limitations under the License.\n",
    "\n",
    "# Preamble to mimick book environment\n",
    "import logging\n",
    "from pprint import pprint\n",
    "from sys import stdout as STDOUT"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello from the child!\n",
      "\n"
     ]
    }
   ],
   "source": [
    "# Example 1\n",
    "import subprocess\n",
    "proc = subprocess.Popen(\n",
    "    ['echo', 'Hello from the child!'],\n",
    "    stdout=subprocess.PIPE)\n",
    "out, err = proc.communicate()\n",
    "print(out.decode('utf-8'))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Working...\n",
      "Working...\n",
      "Exit status 0\n"
     ]
    }
   ],
   "source": [
    "# Example 2\n",
    "from time import sleep, time\n",
    "proc = subprocess.Popen(['sleep', '0.3'])\n",
    "while proc.poll() is None:\n",
    "    print('Working...')\n",
    "    # Some time consuming work here\n",
    "    sleep(0.2)\n",
    "\n",
    "print('Exit status', proc.poll())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Example 3\n",
    "def run_sleep(period):\n",
    "    proc = subprocess.Popen(['sleep', str(period)])\n",
    "    return proc\n",
    "\n",
    "start = time()\n",
    "procs = []\n",
    "for _ in range(10):\n",
    "    proc = run_sleep(0.1)\n",
    "    procs.append(proc)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Finished in 0.167 seconds\n"
     ]
    }
   ],
   "source": [
    "# Example 4\n",
    "for proc in procs:\n",
    "    proc.communicate()\n",
    "end = time()\n",
    "print('Finished in %.3f seconds' % (end - start))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Example 5\n",
    "import os\n",
    "\n",
    "def run_openssl(data):\n",
    "    env = os.environ.copy()\n",
    "    env['password'] = b'\\xe24U\\n\\xd0Ql3S\\x11'\n",
    "    proc = subprocess.Popen(\n",
    "        ['openssl', 'enc', '-des3', '-pass', 'env:password'],\n",
    "        env=env,\n",
    "        stdin=subprocess.PIPE,\n",
    "        stdout=subprocess.PIPE)\n",
    "    proc.stdin.write(data)\n",
    "    proc.stdin.flush()  # Ensure the child gets input\n",
    "    return proc"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Example 6\n",
    "import os\n",
    "procs = []\n",
    "for _ in range(3):\n",
    "    data = os.urandom(10)\n",
    "    proc = run_openssl(data)\n",
    "    procs.append(proc)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "b'\\xc2\\xe1S~\\xab9.s9\\x16'\n",
      "b'\\x8a\\xfb\\xb4\\x90\\xbb<\\xf5\\xdd\\xf4\\x8c'\n",
      "b'b\\x8b9\\x9a4\\xe1\\x91t\\xe22'\n"
     ]
    }
   ],
   "source": [
    "# Example 7\n",
    "for proc in procs:\n",
    "    out, err = proc.communicate()\n",
    "    print(out[-10:])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Example 8\n",
    "def run_md5(input_stdin):\n",
    "    proc = subprocess.Popen(\n",
    "        ['md5'],\n",
    "        stdin=input_stdin,\n",
    "        stdout=subprocess.PIPE)\n",
    "    return proc"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# Example 9\n",
    "input_procs = []\n",
    "hash_procs = []\n",
    "for _ in range(3):\n",
    "    data = os.urandom(10)\n",
    "    proc = run_openssl(data)\n",
    "    input_procs.append(proc)\n",
    "    hash_proc = run_md5(proc.stdout)\n",
    "    hash_procs.append(hash_proc)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "b'c2a92f44b5a5ce1163f0ab8363fc5c0a'\n",
      "b'32fd37d79de4df5c95d3626741b62f04'\n",
      "b'7b00b64a5b5348f9f32e17eb6549d6bc'\n"
     ]
    }
   ],
   "source": [
    "# Example 10\n",
    "for proc in input_procs:\n",
    "    proc.communicate()\n",
    "for proc in hash_procs:\n",
    "    out, err = proc.communicate()\n",
    "    print(out.strip())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exit status -15\n"
     ]
    }
   ],
   "source": [
    "# Example 11\n",
    "proc = run_sleep(10)\n",
    "try:\n",
    "    proc.communicate(timeout=0.1)\n",
    "except subprocess.TimeoutExpired:\n",
    "    proc.terminate()\n",
    "    proc.wait()\n",
    "\n",
    "print('Exit status', proc.poll())"
   ]
  }
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